AQI can change from ridge to ridge and most weather-quality AQI sensors will be in population centers with the vast majority of data in remote areas being an estimate or pulled from public Purple Air PM2.5 sensors (which are surprisingly accurate). YMMV, but any actual long-term exposure above...
I’ve owned all the packs you mention. The K3 is great, and I 100% regret selling mine. Best thing you can do is find one a try it on, because it all comes down to your fit and torso height. I’m a short torso long leg guy and the K3 worked great.